Equine Herpesvirus Infection
There are five equine herpesvirus that are found in the horse environment and are associated with a variety of equine disease syndromes.
EHV-1 causes respiratory disease, the horse shows variable signs which include elevated temperature, nasal discharge, enlarged glands under the jaw and coughing. Some cases may progress to secondary pneumonia and in mares can cause abortions. The virus may cause paralysis in horses of all ages, normally involving weakness of the hind limbs and progressing to all four limbs resulting in death or a requirement for euthanasia.
EHV-2 and EHV-5 normally don´t cause disease on their own but are believed to cause suppression of the horse's immunity to other viral infections and allow them to cause signs of disease, normally respiratory infection.
EHV-3 causes infection of the external genital region characterised by numerous small spots. These burst and become secondarily infected by skin colonising bacteria and then heal leaving pustules.
EHV-4 is a common cause of coughing, loss of performance and abortion in mares. Treatment is usually supportive. Abortion can´t be treated but must be managed, the mare should be isolated from all other pregnant mares because her placenta and placental fluids are highly infectious to other mares after she has aborted.
Herpesvirus spread mainly by inhalation of infectious material and venereally. Horses can be symptomless carriers.
New DNA tests, performed on nasopharyngeal swabs, aborted foetal and placental tissues and cerebrospinal fluid samples, may enable a more rapid diagnosis. Ideally, all horses should be vaccinated against EHV-1 and EHV-4 to reduce the incidence of herpesvirus diseases and to minimise the shedding of virus into the horse environment.
This article is based in scientific veterinary literature.